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  • 1995-1999  (3)
  • 1990-1994
  • Toluene  (2)
  • Neurochirurgie  (1)
  • 1
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Offenes Foramen ovale ; Kontrastechokardiographie ; Neurochirurgie ; sitzende Position ; paradoxe Luftembolie ; Key words Patent foramen ovale ; Contrast echocardiography ; Neurosurgery ; Sitting position ; Paradoxical air embolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Background: The detection or ruling out of a patent foramen ovale (PFO) can be determined noninvasively by contrast echocardiography (CE). The transesophageal technique is superior to the transthoracic technique regarding sensitivity, whereas the specificity of both methods is equally high. This prospective study shows the rational use of transesophageal CE for the detection of a PFO, in patients without cardiovascular disorders. Methods: 165 patients (92 female, 73 male, age 48±18 years) with planned neuro-surgery in a sitting position, underwent CE to rule out a PFO. If the CE was positive, an alternative position was selected in order to avoid a paradoxical air embolism. Results: Initially, a transthoracic CE was performed in all patients resulting in 21 patients (13%) being positive and 39 patients (24%) being negative by sufficient image quality. A transesophageal CE was performed in 96 of the remaining 105 patients (63%). Here, further 25 patients showed a positive CE in the sense of a PFO. The combined use of transthoracic and transesophagel CE revealed a PFO in 46 of 165 patients (28%). Conclusion: The use of both, transthoracic and transesophageal CE is an efficient approach to the preoperative detection of a PFO in the sense of quality and economics. Depending upon the image quality, the use of a transesophageal examination could be avoided in one third of the cases.
    Notes: Zusammenfassung Die präoperative Kontrastechokardiographie (KE) wird zum Ausschluß eines offenen Foramen ovale (PFO) bei Patienten, die einer neurochirurgischen Intervention in sitzender Position unterzogen werden, eingesetzt. Die transösophageale (TEE) KE weist eine höhere Sensitivität in der Diagnostik eines PFO als die transthorakale (TTE) KE auf, während die Spezifität gleich hoch ist. Die Frage der vorliegenden prospektiven Studie war, in wie vielen Fällen die TEE-KE notwendig ist und von welchen Faktoren die Indikation beeinflußt wird. Patienten und Methodik: 165 Patienten (92 Frauen, 73 Männer, Alter 48±18 a) ohne kardiovaskuläre Erkrankungen, die einer neurochirurgischen Operation in sitzender Position unterzogen werden sollten, wurden einer präoperativen KE zum Ausschluß eines PFO zugeführt. Bei allen Patienten wurde zuerst eine TTE-KE durchgeführt. Bei einem positiven Ergebnis wurde auf eine TEE-KE verzichtet. Eine negative TTE-KE wurde lediglich akzeptiert, wenn eine ausreichende transthorakale Schallqualität vorhanden war. In allen anderen Fällen wurde eine TEE-KE angeschlossen. Ergebnisse: Die TTE-KE verlief bei 21 (13%) Patienten positiv und bei 39 (24%) negativ. Bei 105 (63%) mußte aufgrund der insuffizienten Schallqualität eine TEE-KE angeschlossen werden. Dabei wiesen weitere 25 Patienten ein PFO auf. Insgesamt wurden unter der kombinierten Anwendung der TTE-KE und TEE-KE bei 46 Patienten (28%) ein PFO diagnostiziert. In 30% der Fälle konnte auf eine TEE-KE verzichtet werden, wobei der limitierende Faktor der TTE-KE die mangelnde Schallqualität war. Schlußfolgerung: Bei der präoperativen KE zur Diagnostik eines PFO kann in Abhängigkeit von der transthorakalen Schallqualität in 30% auf eine TEE verzichtet werden. Durch einen rationalen Einsatz der TEE-KE können Kosten und unnötige Belastungen des Patienten vermieden werden.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Key wordsThauera ; Toluene ; Benzyl alcohol ; Toluene-oxidizing enzyme system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Toluene and related aromatic compounds can be mineralized to CO2 under anoxic conditions. Oxidation requires new dehydrogenase-type enzymes and water as oxygen source, as opposed to the aerobic enzymatic attack by oxygenases, which depends on molecular oxygen. We studied the anaerobic process in the denitrifying bacterium Thauera sp. strain K172. Toluene and a number of its fluoro-, chloro- and methyl-analogues were transformed to benzoate and the respective analogues by whole cells and by cell extracts. The transformation of xylene isomers to methylbenzoate isomers suggests that xylene degradation is similarly initiated by oxidation of one of the methyl groups. Toluene oxidation was strongly, but reversibly inhibited by benzyl alcohol. The in vitro oxidation of the methyl group was coupled to the reduction of nitrate, required glycerol for activity, and was inhibited by oxygen. Cells also contained benzyl alcohol dehydrogenase (NAD+), benzaldehyde dehydrogenase (NADP+), benzoate-CoA ligase (AMP-forming), and benzoyl-CoA reductase (dearomatizing). The toluene-oxidizing activity was induced when cells were grown anaerobically with toluene and also with benzyl alcohol or benzaldehyde, suggesting that benzyl alcohol or benzaldehyde acts as inducer. The other enzymes were similarly active in cells grown with toluene, benzyl alcohol, benzaldehyde, or benzoate. This is the first in vitro study of anaerobic oxidation of an aromatic hydrocarbon and of the whole-cell regulation of the toluene-oxidizing enzyme.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-072X
    Keywords: Key wordsThauera ; Toluene ; Benzyl alcohol ; Benzyl alcohol dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Toluene and related aromatic compounds are anaerobically degraded by the denitrifying bacterium Thauera sp. strain K172 via oxidation to benzoyl-CoA. The postulated initial step is methylhydroxylation of toluene to benzyl alcohol, which is either a free or enzyme-bound intermediate. Cells grown with toluene or benzyl alcohol contained benzyl alcohol dehydrogenase, which is possibly the second enzyme in the proposed pathway. The enzyme was purified from benzyl-alcohol-grown cells and characterized. It has many properties in common with benzyl alcohol dehydrogenase from Acinetobacter and Pseudo-monas species. The enzyme was active as a homotetramer of 160 kDa, with subunits of 40 kDa. It was NAD+-specific, had an alkaline pH optimum, and was inhibited by thiol-blocking agents. No evidence for a bound cofactor was obtained. Various benzyl alcohol analogues served as substrates, whereas non-aromatic alcohols were not oxidized. The N-terminal amino acid sequence indicates that the enzyme belongs to the class of long-chain Zn2+-dependent alcohol dehydrogenases, although it appears not to contain a metal ion that can be removed by complexing agents.
    Type of Medium: Electronic Resource
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